If you plan to use a ventless fireplace to save money, make sure you consider the safety concerns.

Some service providers say unvented fireplaces burn more efficiently than their vented gas-powered counterparts and cost less to install. Other providers and organizations contend that ventless fireplaces are unsafe or otherwise undesirable.

The National Association of Certified Home Inspectors warns that these fireplaces necessarily vent unburned combustion products - including carbon monoxide - directly into the living space. Although most vent free manufacturers install an oxygen-detection sensor designed to automatically shut the fireplace down if oxygen levels in the home become too low, a lot is riding on that sensor working. NACHI recommends having the unit inspected before use.

Ventless fireplace health risks

While no deaths from vent free fireplace incidents have been reported, NACHI says, some municipalities have restricted or outlawed vent-free fireplaces. The District of Columbia bans the fireplaces in bedrooms and bathrooms, and California banned all ventless fireplaces because of the risks, but no other states outlaw their use.

They put out tons of heat and they're 100 percent efficient, but they use oxygen in the room and put out carbon monoxide, and they smell terrible. It's like a car running in the house.

Ventless fireplace maintenance

On the other hand, some service providers endorse ventless fireplaces. Vent-free fireplaces that are properly installed and serviced annually should function well. There's a lot of training in this industry now, and once it's serviced by someone who knows what they're doing, you shouldn't have problems. But they don't recommend ventless fireplaces for people with respiratory issues, asthma or severe allergies. Generally, they don't recommend combustion products for people with health problems, but for healthy people, if the carbon monoxide sensors are working properly, they would seem to be fine.

Ventless Fireplace Maintenance Tips

- Make sure logs are placed correctly, according to the instructions.

- Have your fireplace inspected annually.

- Make sure your fireplace sensor is free of dust and other particles.

Annual service and proper fireplace maintenance eliminate most dangers. It can be between $175 and $225 for the service, depending on how much cleaning the fireplace requires. Dust and other particles clog the sensor, which need to be cleaned once a year. The logs need to be placed a certain way in the fireplace, which should come with a diagram. If the logs aren't in the right place, it can create black soot, and the logs will produce carbon monoxide.

Real estate agents say vent-free fireplaces don't affect a home's resale value when compared to their vented counterparts, but they add that they'll suggest a vented fireplace if a homeowner needs to choose between the two options. Homeowners usually just see a fireplace, and don't think much about how it operates. Either option provides a return on investmen. "Having a fireplace at all adds value."

If your fireplace requires a gas-line connection, check with your state and/or municipality to see what the licensing requirements are in your area. Some states require the installer to be licensed. Some contractors will install the gas lines, while others won't, so homeowners should ask installers what they're able to do and what their home will need for a vent-free installation. The National Fireplace Institute provides certifications for installers, including a gas specialist distinction for vent-free installers, but the certification isn't required by law.

Cost of ventless gas fireplaces

Services charge around $900 for a ventless fireplace installation that includes gas logs, which typically cost between $200 and $300 if purchased separately. Gas log sets for vented fireplaces cost $1,200 to $1,400.